Hartnell, I love it when people ask me to elaborate because it makes me investigate things further and I always learn stuff! Like this news is actually from April last year!
As for a reliable source... What is that? I honestly don't know which sources to trust and tend to hold to the theory that history was written by the winners and believe that current news is history in the making, influenced and being reshaped at every possible turn.
In saying that, if you Google "Saudi declares atheists terrorists" there are over ten pages of articles - perhaps you have an idea of which sources you would trust. However, because you did ask for an example I decided to share links to the two recorded talks, not because I think they are the most reliable sources, but because they discuss the reasons behind the decision.
http://video.foxnews.com/...atheists-terrorists/
https://www.youtube.com/watch?v=uP_u1Lbpqjk